The invention concerns several methods and several devices for coiling thin metal strip, especially hot-rolled or cold-rolled thin steel strip, on a coiler mandrel, which is adjusted in diameter, in which, at the beginning, the inner windings of the coil are coiled on the adjusted coiler mandrel diameter, and, after the final winding of the coil, the coiler mandrel is pulled out, or the coil is taken off.
Hot-rolled, high-grade thin steel strip is being produced in greater and greater amounts and is now approaching cold-rolled steel strip in both quantity and thickness. This is the result of great advances in the rolling technology of hot-rolled flat strip. It has become economical to produce very thin hot-rolled flat products (ultrathin gages) of less than 2 mm in greater and greater amounts.
Now that the rolling installations are capable of producing such thin hot-rolled flat products, the machines that follow the rolling installations, e.g., the roller table, strip cooling devices, coiler, coil conveyance equipment, and the like, must also be able to meet the new requirements.
A problem that arises during and after the coiling of thin steel strip is that the inner windings of the coil become detached and collapse on themselves. Subsequent winding of the coil onto a coiler mandrel of the uncoiling machine or of another machine for further processing is not possible or is possible only with additional labor and expense. The inner windings of the coil must be cut from the eye of the coil by hand. This manual work reduces the productivity of the plant.
U.S. Pat. No. 5,705,782 describes a spot welding device, which is arranged on a guided support assembly and can be inserted into the eye of the coil to place the weld spots on the inner winding of the coil by electrodes.
In Patent Abstracts of Japan, Vol. 014, No. 478.(M-1036) of Oct. 8, 1990, a method is described in which the steel strip is bonded with a double-sided adhesive tape with the continuous use of a tape-like process material and a special coiling device with a pressing roll to coil the steel strip together with the adhesive tape on a reel. Moreover, no expandable coiler mandrel is provided. Although this makes it possible to prevent the collapse of the inner windings at the beginning of the coiling process, the method is uneconomical in light of the double-sided adhesive tape that is continuously required. In addition, a considerably greater length of steel strip must later be regarded as scrap.
JP 50[1975]-113 456 A, published on Sep. 5, 1975, describes another well-known method. There is no provision for a coiler mandrel with an adjustable diameter. The method involves the use of a punching machine for punching holes by making free punches of flap pieces, such that in each case in a row an upper flap of an outer winding is to be pressed against the next more inner flap of the innermost winding of the eye of the coil. An expandable coiler mandrel could be damaged by the projections that are formed. Here again, collapse of the inner windings of a coil is prevented, but it would be necessary to avoid damage to an expandable coiler mandrel that might be inserted.
The problem of the collapse of the inner winding arises with decreasing strip thickness. Other parameters that have an effect are, for example, material properties, coiler temperature, and strip width. The metal strip no longer has sufficient inherent rigidity and falls into the inside opening of the coil (coil eye) under its own weight and thus reduces the inside diameter of the coil. The problem develops immediately after the coiling of the coil and its removal from the coiler mandrel and intensifies as the coil is further conveyed, until several inner windings have become separated. The aforementioned spot welding method or fastening by welding or by winding on a sleeve is used in the cold rolling and coiling of thin steel strip.